194 OTHER SPOROZOA 



above, are caused by protozoan parasites is very doubtful, and 

 only further investigation can determine the true status of their 

 causative microorganisms. The recent development of knowledge 

 concerning such groups of pathogenic organisms as the Spiro- 

 chsetes and Rickettsia-like organisms, on the border line of visibil- 

 ity, leads to speculation as to whether some of these other diseases 

 may not be found to be caused by parasites of similar nature. 



